Viper burn down.... Help Pls.

Ok pulled the Carb. bowls this AM, quick look but they seemed good. I'll do a more indepth inspection tonight.

Here is the seal, I'm begining to lean this direction but like I said really hard to tell if this was cause or effect of my failure.
 

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mopar1rules,

Detonation DOES create intense LOCAL heat. Heat alone without detonation creates damage in more than one area, sometimes melting sides of the piston and leaving the top intact.

I raced v-8s for decades and built my own engines, cant tell you how many times I have seen detonation damaged pistons as we always ran on the edge.

I can see that you do not believe me so I am including a link and some data. Feel free to do your own research if you still doubt.

http://www.theultralightplace.com/pistons.htm

The piston shows melted areas on the dome and seizure marks on the skirt.

Detonation results in extremely high combustion chamber temperatures. That rapid heat rise, if allowed to continue, will heat combustion chamber deposits and spark plug electrodes to the point that they will ignite the charge before the spark at the plug does.

This condition is called runaway surface ignition or pre-ignition. Once pre-ignition occurs, the temperature rise is so rapid that melting point of the piston is reached while the engine is still running. Metal will melt away beneath the spark plug or in areas of high heat retention such as at the ring positioning pin.

A complete breakdown of the lubrication film also occurs resulting in severe seizure. Detonation always precedes pre-ignition and the causes for this abnormal combustion are the same as those for detonation.
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Vipers have a known water flow issue especially on the mag side cylinder. To answer vmaxmike get the aftermarket head if you can or do like I did and get the Opticool head gasket from Bender. That and set needles to next setting. I have my needles set to 3.5 even thoutgh I run at over 10k altitude.
 
vmaxmike,
Please do your research. I would really hate to see you assemble your engine and repeat this failure.

Do a search on my user ID and see the thread where I went through this. Viper engine was an SRX redesign and they made a huge mistake with the head. Look at the head and note the water exit port. When I saw that I assumed Yamaha had altered water flow internally to solve the obvious flow probelm. Well, they did not.

Put like this. Hold two garden hoses and point them in a Y. Good flow right? Now point them at each other at the angle you see the water flow in your Viper head from cylinder 3 against cylinder 1 and 2. Big problem eh?

Bender has a head gasket with altered flow to solve this issue by evening up water flow.

But how can this cause detionation? Isn't detonation caused by bad fuel? NO, not always. Poor water circulation can cause metal in one spot to overheat and act like a glow plug on a diesel engine. Causes fuel to ignite before it should causing detonation. Buckle this with fuel of poor quality this year and you can see why Vipers are dieing like flies...lol.
 
I plan to get that head gasket figure it can't hurt.... :) I talked to the pervious owner last night and he said It just seemed to not run right this year from the the first time he lit it and this happened on his first trip out.

It will be hard to say exactly what did this but at this point I'm begining to think the seal caused it. I agree the Mag cyl. could have been detonation but seeing the other two scored as well I think she was lean.

M
 
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Pressure Test Engine

The best way to test an engine for air leaks is to pressure test it. If after doing a post-mortem I can't determine why the engine blew I do a pressure test. I usually go through the carbs and pressure test before disassembly. It will indicate if the seals are leaking down, carb boots etc. are not holding air and repair as required. It is always a good idea to retest after the rebuild. You can use expansion plugs for sealing the carb boots and exhaust ports. If the exhaust ports are oval as in the viper I use fabricated plates to seal them.
My buddy and I are doing this, this afternoon on his son's viper as it lost a the center cylinder and we are reassemblying it. When going through the carbs the center pilot jet was plugged solid and we are blaming that as cause of failure. But you can't be to careful. Good luck with yours Mike!
 
vmax535, A plugged pilot jet will not burn down a healthy engine with a healthy cooling system. I have cleaned dozens of carbs for a local motorsports store over the years that did not burn down. BUT, a Viper with known head problems is weak already and yeah...a plugged pilot jet could tip an already weak system over the edge.

Ignore the head problems on a Viper at your own peril.
 
stingray, i know you talk of the poor head design causing deto, but i find it kinda funny then how my piped/ported viper never gave me fits in the 5000+ miles that are on it, w/the stock head.
 
stingray719 said:
vmax535, A plugged pilot jet will not burn down a healthy engine with a healthy cooling system.
Click to expand...

Generally I agree with your opinion but have not been able to determine any other root cause of failure.
This motor has a peak performance 12:1 head, bender triples, v-force reeds, stock porting and timing, 162.5 mj, 50 pilots, needles in #4 position and runs shell 91 none ethonol fuel.

The day that it failed it was doing alot of low speed towing. The rider said one cylinder would drop or not fire at all below 4500 - 4700 rpm then would pick up above that rpm. It made sense to me that the cylinder would fire once it got onto the needle jet. But would not receive any fuel through the pilot circuit below approx. 1/4 throttle causing a low speed lean condition and eventually detonation.

This is just a theory. And is only coincidence that the cylinder that failed had a clogged pilot jet? It's hard to be sure.
 
Got through the carbs tonight.... Mag & center Pilots 100% plugged no light and couldn't blow through them.

Sewing needle and compressed air needed to open them, bowls were spotless though?

Anyway i'd say this is main factor, at this point who knows...? but i'm gonna blame the carbs and say the seal got cooked by the meltdown.

I'll be re-assembeling with an Opticool gasket and installing a SRX rear cooler.
 
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